marko/src/translator/util/optimize-html-writes.js

UI Components + streaming, async, high performance, HTML templating for Node.js and the browser.

import { normalizeTemplateString } from "@marko/compiler/babel-utils";

const mergeWriteCallsVisitor = {
  ExpressionStatement(path) {
    let curPath = path;
    const quasis = [""];
    const expressions = [];
    const removals = [];

    do {
      const content = getOutContent(curPath);
      if (!content) break;
      if (curPath !== path) removals.push(curPath);
      quasis.push("");
      expressions.push(content);
    } while ((curPath = curPath.getNextSibling()));

    removals.forEach((removal) => removal.remove());

    if (expressions.length > 1) {
      path
        .get("expression.arguments.0")
        .replaceWith(normalizeTemplateString(quasis, ...expressions));
    }
  },
};

export function optimizeHTMLWrites(path) {
  const {
    hub: {
      file: { markoOpts },
    },
  } = path;

  if (markoOpts.optimize && markoOpts.output === "html") {
    path.traverse(mergeWriteCallsVisitor);
  }
}

function getOutContent(path) {
  if (path.isExpressionStatement()) {
    return getOutContent(path.get("expression"));
  }

  return (
    path.isCallExpression() &&
    path.get("callee").isMemberExpression() &&
    path.get("callee.object.name").node === "out" &&
    path.get("callee.property.name").node === "w" &&
    path.get("arguments.0").node
  );
}